The Dells Off-Trail Trek field trip with the Natural Resources Foundation takes participants on a strenuous hike through areas of the Dells of the Wisconsin River State Natural Area that are not normally accessible to the public. Michelle Milford

Participants on a Natural Resources Foundation trip take photos of a beaver lodge on May 16, 2013, on the Lower Wisconsin State Riverway near Blue River. Each year the foundation offers hundreds of trips in state parks, natural areas and other locations. Mark Hoffman/Milwaukee Journal Sentinel

Participants on a Natural Resources Foundation trip paddle on the Lower Wisconsin State Riverway near Blue River on May 16, 2013. Each year the foundation offers hundreds of trips in state parks, natural areas and other locations. Mark Hoffman/Milwaukee Journal Sentinel

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When the Natural Resources Foundation of Wisconsin opened registration for its field trips last year, they filled to 70% capacity within a day.

The popular field trips are offered April through November and are open only to members of the nonprofit organization. They take participants to every corner of the state, from hikes in secret corners of popular state parks and paddles in voyageur canoes to treks to see rare Karner blue butterflies or little Kirtland’s warblers.

The NRF started with three trips in 1993 and since then has taken more than 50,000 participants on more than 2,600 trips to every county in Wisconsin. This year the foundation is offering 234 trips showcasing the diversity of Wisconsin’s flora and fauna.

“One of our beliefs at the foundation is that nature has inherent value and that people have an ability and desire to make a positive difference for Wisconsin’s lands, waters and wildlife. I feel like the field trip program is vital to that,” said Christine Tanzer, who has directed the field trip program for more than 20 years.

“It really gives people a sense of the unique diversity of habitats in Wisconsin,” she said. “We live in an amazing place.”

Kayakers paddle through the Dells of the Wisconsin River on a field trip with the Natural Resources Foundation of Wisconsin.(Photo: Patty Henry)

While some trips fill up fast, there are more than 6,000 spots available, Tanzer said, so there are “still always good trips throughout the whole season.”

That includes more than 76 family-friendly trips, and accessible trips for participants with limited mobility. The foundation’s Field Trip Guidebook color-codes trips by difficulty.

“Because there’s so much, I feel like it gives you an overview of the diversity of Wisconsin’s natural resources, and hopefully people learn something as they go through,” she said.

“Some of the trips are to places where people have never been," she said. “It’s also an opportunity for people to go to places maybe they’ve been to before, but it gives them a new experience and a new understanding” of that familiar place, she said.

Trip leaders play a vital role in providing that new perspective, she said — many work for the DNR and are at the front lines of conservation work in the state.

She said while “the heart of the program is lifelong learning” — i.e. adults who have a career in something else but a passion for the outdoors — she loves seeing grandparents bring their grandchildren on trips.

Getting kids into nature is part of the foundation’s mission, which also includes providing grants for managing state natural areas and endangered species. The NRF has given more than $7.2 million to such efforts and has been instrumental in helping the recovery of species like trumpeter swans.

Participants in a field trip sponsored by the Natural Resources Foundation of Wisconsin look for trumpeter swans July 16 near Babcock.(Photo: Patrick Durkin/For USA TODAY NETWORK-Wisconsin)

Registration for the trips opens for members at noon on March 27 at wisconservation.org. Membership donations start at $25.

Here are some trips to consider this year. Trips listed here include their number in the Field Trip Guidebook, which is available on the NRF’s website.

Secret spots

Some field trips offer the chance to see areas not normally open to the public or go off-trail to explore popular parks in a new way.

The Dells Off-Trail Trek on May 17 (No. 39, $40) is one of the NRF’s most popular trips. Led by DNR conservation biologist Thomas Meyer, the strenuous hike travels through gorges, glens and bluffs in the Dells of the Wisconsin River State Natural Area that are not normally accessible to the public.

Devil’s Lake State Park is the state’s most popular park, but most visitors stick to the bluff trails. The Power Trek to the Devil’s Nose trip on June 7 (No. 72, $30) takes participants on a challenging, 4-mile off-trail hike through the South Bluff/Devil’s Nose SNA in the park.

Off the Beaten Path at Peninsula State Park on Aug. 23 (No. 183, $15) takes participants to less-visited sites in the popular Door County park, including an abandoned Civilian Conservation Corps camp and the old Blossumburg Cemetery.

Birdwatchers have a rare chance to visit Green Bay’s Cat Island, which is normally not open to the public, during Shorebirds & Waterbirds of Cat Island on Aug. 17 (No. 175, $100).

Bird watchers look for birds in the Tiffany Wildlife Area. The remote area is reachable via a train ride that is offered a handful of times every spring and fall.(Photo: RJ & Linda Miller)

The NRF helped provide funding to restore the Lower Chippewa River in the Tiffany Wildlife Area in Buffalo County. Two trips take participants to remote, difficult-to-access spots in the wildlife area via a train: Train Ride & Birds: Tiffany Wildlife Area & Lower Chippewa River (No. 28, May 11, $40) and Train Ride & Bluff Prairie Hike: Tiffany Wildlife Area (No. 203, Sept. 14, $48).

Wisconsin is home to 40 native orchids, and 26 grow in The Ridges Sanctuary in Baileys Harbor. Learn about them during Orchids in the Boreal Forest of Door County on June 20 (No. 94, $25).

A desert in a Great Lakes state? See the unique landscape, which includes prickly pear cacti and sand dunes, during Wisconsin's Desert: Blue River Sand Barrens SNA on June 28 (No. 111, $20) or Sept. 7 (No. 197, $15).

To the Bat Cave! Kickapoo Caverns (No. 150, $40/adults, $30/kids 8+) takes participants into one of the state’s largest caves, home to a bat hibernaculum, in Crawford County on July 27.

The Cedarburg Bog became the state’s second natural area in 1952; it’s the most southern string-bog in the country and is a National Natural Landmark. Hike it at dusk on the Cedarburg Bog SNA: History, Woodcocks & Frogs trip on April 24 (No. 5, $18/adults and $8/kids 10+).

Rush Creek SNA: Blooms, Birds & Breathtaking Vistas was one of the NRF’s original three field trips. Explore the dry-prairie bluff along the Mississippi River in Ferryville during spring migration on May 17 (No. 38, $15).

Hike the nation’s first Tribal National Park during Frog Bay Tribal National Park: Old Growth and Birding in Red Cliff on June 1 (No. 60, $35). The trip will be co-led by members of the Red Cliff Band of Lake Superior Chippewa and will take participants through the park along Lake Superior, with views of the lake’s famous Apostle Islands.

Unique animals

Lake Sturgeon: Lifting Nets on Lake Superior on May 16 and 17 (No. 37, $50) lets participants work with DNR biologists to handle ancient sturgeon, which can grow up to 9 feet long and live more than 50 years.

Whooping Crane adults and young seen at Necedah National Wildlife Refuge.(Photo: Courtesy Cathy Carnes)

In 2001, whooping cranes were reintroduced to Wisconsin, and the flock has been growing since. See some of them in the wild on the Whooping Crane Reintroduction trip at the Necedah National Wildlife Refuge on May 18 (No. 48, $60), or go behind the scenes at the International Crane Foundation during Creating Spaces for Crane Conservation in Baraboo on Sept. 27 (No. 213, $25).

Search for one of Wisconsin’s rarest birds during Kirtland’s Warblers Up Close in protected pine barrens in Adams County on May 22 (No. 53, $45).

The haunting call of the loon is a sign you’re in Wisconsin’s Northwoods. Learn about the bird and stop at several lakes to see it during Symbols of the Northwoods: The Common Loon in Eagle River on June 1 (No. 61, $30).

The Mecan Prairie in Marquette County features more than 170 acres of restored prairie and savanna, and it should be in bloom June 6 for Spring Prairie Flowers & Karner Blue Butterflies (No. 67, $25). Participants can see the endangered butterfly whose caterpillars feed only on wild lupine.

Paddling trips

Aside from hiking, paddling is one of the most popular activities for NRF field trips.

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The Eagle Banding & Voyager Canoe on the Lower Wisconsin River trips on May 3 and 4 (No. 14, $115) is one of the most popular, since it is a small, intimate paddle (just 15 people per trip) down the Wisconsin River in Grant County to an eagle nest. There participants help DNR biologists band eaglets.

The Door County Kayak Wetlands Tour on June 1 and 8 (No. 62, $55/adults, $45/kids 10+) is great for beginners and takes participants on Reiboldts Creek, one of the cleanest creeks in the state.

The Wild Edibles Paddle on the Yellow River on June 4 (No. 66, $25) is for experienced paddlers and includes instructions on safe foraging for edible plants that grow along the river.

Birding, Boating and Breweries along the Milwaukee River on June 14 is also for experienced paddlers, taking them along the river from Waubedonia to Grafton to finish at a brewpub there (No. 87, $15).

For another slice of the river, the Milwaukee River Greenway: Hike & Paddle on June 15 (No. 93, $30) takes paddlers on a hike along the Milwaukee River Greenway, a paddle on the Greenway Water Trail and finishes with grilled sausages and local beer.

The “Boundary Waters” Canoe Experience in Washburn County takes paddlers on five wilderness lakes along the Sawmill Lake Canoe Route during peak fall color on Oct 5 (No. 218, $35).

Learn a new outdoor skill

Go beyond hiking and paddling and learn something new on these trips.

Photography and outdoor exploration go hand in hand. Learn how to capture birds in flight from Sunil Gopalan, who has been published in National Geographic magazine, during the Bird Photography Workshop in Waupun on May 11 (No. 26, $100). Or sharpen your flower photography skills during Wildflower Nature Photography in Sussex on July 20 (No. 134, $20) or near the Retzer Nature Center in Waukesha on July 27 (No. 145, $20).

Cathedral Pines State Natural Area in Oconto County includes one of the best stands of old-growth pine and hemlock trees in the Chequamegon-Nicolet National Forest. Chelsey Lewis/Milwaukee Journal Sentinel

Holy Hill isn't officially part of the Kettle Moraine State Forest, but it sits atop a kame in the glaciated terrain and provides views from one of the highest spots in southeastern Wisconsin. Mike De Sisti/Milwaukee Journal Sentinel

The Ice Age Trail travels more than 31 miles through the length of the Kettle Moraine State Forest-Northern Unit, which is a vibrant green in the early summer thanks to abundant spring rains. Chelsey Lewis/Milwaukee Journal Sentinel

Big Falls tumbles 10 feet over a rock ledge along the Eau Claire River at Big Falls County Park outside of Eau Claire. The river drops over a number of rock ledges and around small islands at the park, which also features a small sandy beach. Chelsey Lewis/Milwaukee Journal Sentinel

The St. Croix River cuts through a basalt gorge known as the Dalles of the St. Croix in St. Croix Falls. The dramatic rock walls are part of Interstate State Park — both on the Wisconsin and Minnesota sides of the river. Chelsey Lewis / Milwaukee Journal Sentinel

Stout's Island Lodge was built in 1912 as a private island retreat for the family of Frank Stout, one of Chicago's wealthiest men. Today the resort is open to overnight visitors in the summer. Chelsey Lewis/Milwaukee Journal Sentinel

Workers used dynamite, hand tools, horses, mules and oxen to build this tunnel for the Chicago and North Western railroad in 1873. Today the tunnel is a path for cyclists and hikers as part of the Elroy-Sparta State Trail. Chelsey Lewis/Milwaukee Journal Sentinel

Tunnel 1 on the Elroy-Sparta State Trail is 1,694 feet and was completed in 1873. Doors on the tunnels are closed in the winter to keep the inside warmer and prevent freezing and thawing that could cause rocks to fall and block the entrances. Chelsey Lewis/Milwaukee Journal Sentinel

The boathouse and Viking Hall greet visitors to Rock Island State Park north of Door County. The building was constructed using limestone from the island in 1928. Chelsey Lewis/Milwaukee Journal Sentinel

At Copper Falls State Park near Mellen, there are two falls to choose from, Copper Falls (pictured here) and Brownstone Falls. Both are easily viewed from trails around the gorge, but close access is difficult because of the steep cliffs. Journal Sentinel files